Cultivating device

ABSTRACT

A cultivator for aerating a ground surface. The cultivator has a support frame moveable relative to the ground surface and a follower first pivotally connected to the support frame by a first pair of spaced link arms. The link arms have two pairs of equidistantly spaced pivot points for linear movement of the follower in a first direction away from the support frame. A tool support member is pivotally connected to the follower by a second pair of spaced link arms. The second link arms have two pairs of equidistantly spaced pivot points for linear movement of a cultivating tool in a second direction substantially perpendicular to the first direction. A driver effects cyclic movement of the tool support member in the second direction and movement of the follower in the first direction. A bias element provides resilient damping of the movement of the follower along the first direction away from the support frame, wherein the resilient damping is provided at an extremity of movement of the follower outward from the support frame along the first direction, to urge the follower in the direction of inward movement toward the support frame. A dampening element provides resilient damping of the movement of the follower along the first direction toward the support frame, the resilient damping provided at an extremity of movement of the follower inward toward the support frame in the first direction to progressively arrest movement of the follower in the direction of inward movement toward the support frame.

FIELD OF THE INVENTION

This invention relates to a cultivator for aerating ground surfaces. Theinvention has particular application to cultivators for aerating turfsurfaces, such as golf courses, sporting grounds, bowling greens and thelike.

BACKGROUND ART

Cultivators of this type are used for maintaining landscaped groundsurfaces, including turf. In this sense the term “turf” refers to grassand other material which is specifically grown for playing sport andused for example to form golf course greens, sporting fields and bowlinggreens. Cultivators are frequently used on these types or surfaces forrepeatedly penetrating the ground surface, forming a plurality of holesso that the ground surface is aerated, to improve growth of the grass orother material and enhance the condition of the surface for playingpurposes.

In conducting this type of aeration of turf surfaces, the neatness ofthe edges of the hole made by the cultivator can significantly affectthe overall result. For example in the case of golfing or bowling greensand the like where the vegetation is short, a hole with rough edges ortoo large a hole can cause spot erosion, resulting in an undesirabledimple in the ground surface. This effect is aggravated when the forwardmovement of a cultivator differs from the speed of the hole-making toolover the ground surface, causing the hole-making tool to “break” theground surface. Often this problem is encountered in cultivators poweredby a link to a prime mover (such as a tractor), where difficulties insynchronising the speed of the hole making tool with the speed of theprime mover, arises, for example due to different gear ratios betweenthe driving wheels of the tractor and the power link.

One known cultivator described in Australian Patent Application 73500/87has a structure mounted on ground engaging wheels with tool supportmeans mounted on the frame so that the tool support means is moveablerelative to the structure. A cultivating tool, usually a tine or seriesof tines is mounted on a flat plate so that the tine(s) are relativelyvertical to the plate. The plate is mounted on the tool support meansvia a pair of link arms so that the plate (and vertical tines) freelypivots relative to the tool support means.

As the cultivator moves forward along the ground surface (via a primemover), the fly wheel drives one end of the tool support member in acircular path. This causes the other end of the tool support means tomove in a reciprocating motion so that the cultivating tool isrepeatedly forced into the ground surface. This cycle of reciprocatingmotion of repeated penetrations by the cultivation tool is used toproduce holes and is generally referred to as an aeration time cycle.The horizontal plate freely pivots about the tool support means via linkarms, so that the cultivating tool tends to be substantially verticaldespite the rotation of the fly wheel during the aeration time cycle.Accordingly, the cultivating tool is kept substantially vertical forentry and withdrawal from the ground surface as the link arms will pivotto compensate for forward motion of the cultivating device. That is, ateach part of the cycle in which the tool is withdrawn from the groundsurface, the freely pivoting link arms positions the cultivation tool ina substantially vertical position for the next cycle of penetration intothe ground. This means that fairly neat holes are produced in the groundthrough this flywheel arrangement.

While this cultivator achieves fairly neat holes in ground surfaces suchas turf, the free pivoting arrangement of the cultivation tool restrictsthe depth of holes that can be produced. This is at least partly theresult of the above described cultivator not being suitable for scalingup in size. If this cultivating device is directly scaled up to a largermachine to provide deeper holes, the number of holes in a given surfacearea would reduce because the distance between holes formed by thecultivating tool would also be scaled upward. The distance between theseholes would increase because the necessary scaling up of the size of theflywheel is to increase vertical travel of the cultivating tool. Whileit has been proposed to use a plate of increased area to cover thisincreased distance (using a larger number of tines per plate), suchplates are unwieldy and awkward as well as requiring greatly increasedpower to effect penetration of the larger number of tines.

DISCLOSURE OF THE INVENTION

It is an object of this invention to provide a cultivator for aerating aground surface that will overcome one or more of the above disadvantagesor at least provide a useful alternative.

According to an aspect of the invention, there is provided a cultivatorfor aerating a ground surface including:

-   -   a support frame moveable relative to the ground surface;    -   a follower pivotally connected to the support frame by a first        pair of link arms having two pairs of equidistantly spaced pivot        points for linear movement of the follower in a first direction        away from the support frame;    -   a tool support member pivotally connected to the follower by a        second pair of link arms having two pairs of equidistantly        spaced pivot points for linear movement of a cultivating tool in        a second direction substantially perpendicular to the first        direction;    -   and a driver to selectively effect cyclic movement of the tool        support member in said second direction and effect movement of        the follower in said first direction at a substantially constant        rate during at least a selected portion of said cyclic movement        corresponding to ground engagement of the cultivating tool.

The link arm arrangement of the cultivator device allows the followerand the tool support member to linearly move in the second directionduring engagement with the ground surface as the support frame movesover the ground surface. That is, the first and second pairs of linkarms compensate for the increasing distance between the support frameand the tool support member caused by the support frame moving along theground surface so that the tool support member is effectively stationarywhen the cultivation tool is engaged in the ground surface.

Preferably, the first direction is substantially parallel to the groundsurface while the second direction is preferably substantiallyperpendicular to the ground surface. In this form of the invention, thetool support member is kept substantially perpendicular relative to theground surface when penetrating and withdrawing from the ground surface.This in turn ensures that a substantially perpendicular hole isproduced, avoiding any ragged edges and undesirable pressure on the sidewall of the tined hole.

In addition, the cycle time can be varied quite easily by increasing thefrequency in which the driver operates (hereinafter referred to as the“driver frequency”), thereby producing more holes in a given surfacearea. There is no tendency for the tine to propel the cultivator so thatif the cultivator device is scaled up in size, the driver frequency canbe increased to ensure that the same number of holes for a given surfacearea is produced, compensating for the larger distance between “hits”.This avoids the difficulty in scaling up of the known cultivator wherethe flywheel radius imposes a physical constraint.

The first pair of link arms preferably maintains the follower in a fixedor constant orientation to the support frame. It is preferred that thefirst pair of link arms are substantially parallel to each other. Onelink arm of the first pair of link arms may be pivotally connected tothe support frame via a support arm. One or more of the first, pair oflink arms can be bent to form an included obtuse angle.

Preferably, the second pair of link arms are substantially parallel toeach other. In a preferred embodiment, the follower, second pair of linkarms and the tool support member substantially form a parallelogram. Thetool support member forms the side of the parallelogram furthest fromthe support frame. One or more or each the first and second link armscan be formed by two parallel elements.

The driver is preferably pivotally connected to one link arm of thesecond pair of link arms. The driver can lie substantially parallel toone link arm of the first pair of link arms when effecting selectivecyclic movement in the second direction.

The driver can be pivotally connected to the support frame. It ispreferred that the driver is mounted to the support frame via a supportarm. The driver is preferably mounted to the same support arm thatpivotally connects one link arm of the first pair of link arms. In apreferred embodiment, driver and the link arm can be arranged on thesupport arm so that they are substantially parallel to each other.

In one embodiment the driver is a linearly operable device such ashydraulic or pneumatic cylinder controlled by a hydraulic or pneumaticcircuit. In another embodiment the driver is a mechanical arrangementwhich imparts reciprocating movement to the link arm assembly.Preferably, the mechanical arrangement includes a flywheel and aconnecting rod. The connecting rod is preferably connected to one of thefirst pair of link arms. The flywheel is preferably driven in rotationby a suitable power source, for example by vee belt connection. Theconnection between the drive and link arm assembly, for example thehydraulic cylinder or connecting rod is preferably arranged to aid thedesired overall movement in the first direction during each part of thecycle of operation. That is the driver connection preferably aidsmovement of the tool support away from the support frame during at leastpart of the cycle time in which the ground is engaged. More preferably,the movement is aided at the critical time on the upstroke as the toolis emerging from the ground. Preferably the driver connection also aidsmovement of the tool support toward the support frame at the end of thecycle following completion of ground engagement.

It is preferred that a bias element is located between the follower andthe support frame for assisting the follower to be returned to a restposition in the cycle. It is preferred that the bias element is locatedat the junction between the support frame and the link arm. The biasmember can in one form of the invention engage one end of the link arm.

In one embodiment a stop is located on the follower for dampening forcesproduced by the driver in returning the follower to the rest position.The stop is preferably located at one corner of the parallelogram. Thecorner is preferably the corner that is closest to both the supportframe and the ground surface.

In another embodiment of the invention a dampening block is arranged ina position to prevent bounce when the tool is returned to the top ofstroke position by the bias element. A cam surface carried by one of thelinks rotates to engage the dampening black to arrest the rebound orbounce as the tool returns to its top of stroke position.

In one form of the invention the support frame can include groundengaging wheels for moving along the ground surface. Equally however thecultivator can be in a form suitable for mounting to the three-pointlinkage of a tractor. In this case the tractor can supply driving powerto the cultivator either hydraulic power from an auxiliary hydraulicoutlet on the tractor or mechanical power from the tractor powertake-off.

Numerous other advantages and features of the present invention will bebecome readily apparent from the following detailed description of theinvention and the embodiments thereof, from the claims and from theaccompanying drawings.

To assist in the understanding of the invention, some embodiments of theinvention will now be described by way of example only, with referenceto the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a cultivator according to a first embodiment ofthe invention;

FIG. 2 is a view of the other side of the cultivator of FIG. 1;

FIG. 3 is a perspective view of part of the cultivator of FIG. 1;

FIG. 4 is a perspective view of a further part of the cultivator of FIG.1;

FIG. 5 is a schematic diagram of a hydraulic circuit forming part of thecultivator of FIG. 1;

FIG. 6 is a side view of the link arm assembly of the cultivator of FIG.1 at the beginning of an aeration cycle;

FIG. 7 is a side view of the link arm assembly of FIG. 6 at the point ofground engagement in the aeration cycle;

FIG. 8 is a side view of the link arm assembly of FIG. 6 at mid depthduring ground engagement in the aeration cycle;

FIG. 9 is a side view of the link arm assembly of FIG. 6 at full depthof ground engagement in the aeration cycle;

FIG. 10 is a side view of the link arm assembly during withdrawal fromground engagement in the aeration cycle;

FIG. 11 is a side view of the link arm assembly of FIG. 6 at the pointof disengagement of the ground in the aeration cycle;

FIGS. 12 and 13 are side views of the link arm assembly of FIG. 6illustrating operation where the cultivation tool strikes an obstructionduring the aeration cycle;

FIG. 14 is a side view of a link arm assembly similar to FIG. 6 showinga second embodiment of the invention;

FIG. 15 is side view of a link arm assembly similar to FIG. 14 showing athird embodiment of the invention; and

FIG. 16 is an enlarged, fragmentary side view of the third embodiment.

BEST MODES OF CARRYING OUT THE INVENTION

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings, and will be described herein indetail, specific embodiments thereof with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the specific embodiments illustrated.

FIGS. 1 to 13 show a cultivating device 1 for aerating ground surfacesaccording to one embodiment of the present invention. The cultivatingdevice 1 has support frame 2, to which ground engaging wheels 3 aremounted for moving the cultivating device along the ground surface. Thecultivator is of the tricycle type with two drive wheels 3 and asteering wheel 3 pivotally mounted to frame 2. A handle arrangement 4provides for control of the steering wheel 3 by an operator and alsoprovides a convenient location for mounting of cultivator controls (notshown). An engine 5 is mounted on the support frame 2 to drive thecultivating device 1 across the ground via one or more of the wheels 3and to drive a hydraulic system described below. The drive of wheel 3 isof conventional type through a gearbox (not shown) and appropriatesprockets 6 and 7 and chains 8, 9. This drive system is of the typeknown to those skilled in the art and will not be described in detail.Arrow A shows the direction of normal travel of the cultivator.

Engine 5 also drives a hydraulic pump 10 supplied with hydraulic oilfrom a reservoir 11 via pipe 12. Any suitable hydraulic component can beused to supply hydraulic pressure for operation of the hydraulic systemdescribed below. Hydraulic pressure from pump 10 is supplied via pipe 13to a distribution manifold 14 which provides hydraulic pressure tosolenoid valves 15 and flow control valves 16 for operation of hydrauliccylinders 17. An electronic control system 18 is provided for operationof the hydraulic system.

Four identical link arm assemblies 19 are mounted to frame 2. FIG. 3 isa detailed perspective view of one of the assemblies 19. FIG. 4 is aperspective view of the four assemblies omitting some of the detail ofFIG. 3 for clarity. Each of the link arm assemblies mounts a pair ofcultivation tools 20 only one of which is visible in the side views.

Each of the assemblies 19 has a base plate 21 which provides a mountingto support frame 2. A pair of link arms 24, 25 pivotally mount afollower 26 with the base plate 21. Upper link arm 24 is formed of twoparallel elements 24 a and 24 b. Link arm elements 24 a and 24 b aremounted to a fixed support arm 22 that extends from base plate 21 by apivotal connection at 27. The other ends of link arm elements 24 a and24 b are pivotally connected to the follower 26 at pivot point 28. Lowerlink arm 25 is generally U-shaped and has two parallel elements 25 a and25 b. A first end of link arm 25 is mounted with base plate 21 by apivotal connection at 29 to a housing 30 fixed to the base plate 21. Theends of link arm elements 25 a, 25 b are pivotally connected to thefollower 26 at pivot point 31. In this way link arms 24 and 25 arespaced and have pairs of equally spaced pivot points (27, 28, 29, 31).This results in follower 26 being mounted for linear movement in a firstdirection toward and away from support frame 2 to which base plate 21 ismounted. By making the pivot points 27, 28, 29 and 31 coincide with thecorners of a parallelogram the orientation of follower 26 with respectto the support frame 2 is maintained throughout this linear movement. Asbest seen in FIG. 6 link arm 25 is bent to form an obtuse angle.

A second pair of link arms 32, 33 pivotally mounts a tool support 34outwardly from the follower 26. Link arm 32 is made up of two link armelements 32 a, 32 b connected with the follower at pivot point 28. Theother end of link arms 32 a, 32 b is pivotally connected at 35 to theupper end of tool support 34. Link arm 33 is also made up of twosubstantially parallel link arm elements 33 a, 33 b mounted withfollower 26 at pivot point 31. The other end of link arms 33 a, 33 b isconnected at pivot point 36 to tool support 34. Cultivator tools ortines 20 are mounted to the lower end of tool support 34. Pivot points28, 31, 35 and 36 substantially lie on the corners of a parallelogramand link arms 32, 33 follower 26 and tool support 34 substantially formthe sides of the parallelogram. This provides for a linear movement ofthe tool support member 34 in a direction perpendicular to the directionof movement of follower 26. That is, upwardly and downwardly withrespect to the support frame 2 to which base plate 21 is mounted. Thismaintains the orientation of tool support 34 with respect to follower 26throughout its range of movement. Thus if follower 26 is mounted so asto be perpendicular to the ground surface supporting the cultivator 1,tool support 34 moves upwardly and downwardly perpendicular to thatsurface. At the same time the first link arms 24, 25 allow movement ofthe follower 26 and hence tool support 34 toward and away from thesupport frame whilst vertical orientation is maintained.

It will be apparent that the first pair of link arms 24, 25 need not beparallel to each other so long as their respective pivot points areequidistant. Similarly, it is also within the scope of this inventionthat the second pair of link arms 32, 33 need not be parallel to eachother but maintain their pivot points equidistant to each other. Theparallelogram structure described above has been found to be the mostsuitable and convenient manner to meet this requirement of equidistantlyspaced pivot points.

A driver in the form of a hydraulic cylinder 17 is provided to driveeach of the linkage assemblies 19. One end of the hydraulic cylinder 17is connected at pivot point 38 to an extension 23 of fixed support arm22. A L-shaped bracket 39 connects the other end of hydraulic cylinder17 to the upper link arm 32 at pivot point 40. In this way the hydrauliccylinder 17 effectively acts between the support frame (via base plate21 and support arm 22) and the link arm 32.

The pivot points are arranged such that a line joining pivot points 27and 28 is almost parallel to the line joining pivot points 38 and 40.The cylinder 17 and link arm 24 are arranged on the support arm 22 sothat the cylinder 17 and link arm 24 are substantially parallel to eachother. The pivot point 40 on support arm 32, which joins the cylinder 17to link arm 32, determines the maximum outward extension to which thecylinder 17 may move link arm 32 relative to the support frame 2.

A bias element 41 is provided in housing 30. The link arm 25 has a pedallike extension 42 for engaging the bias element 41 to provide resilientdamping at the extremity of movement outward from the support frame 2.This assists in urging the assembly 19 inward toward the support framewhen it reaches the extremity of travel. A second element 43 is providedat the opposite side of the extension 42 to act as a resilient stop whenthe link arm assembly 19 moves back to the extremity of movement inwardtoward the support frame 2.

A stop 44 mounted by a bracket 45 on the link arm 33 for dampening theforces produced by retraction of the cylinder 17 in returning thelinkage assembly 19 to the rest position.

FIG. 5 shows a schematic drawing of the hydraulic circuit 50 used forthe control of hydraulic cylinder 17. As described above a motor 5drives pump 10 to supply hydraulic fluid from a reservoir 11 to amanifold 14. The supply lines 12 and 13 shown in FIG. 2 are also shownrespectively connecting reservoir 11 to pump 10 and pump 10 to manifold14. Supply of hydraulic pressure to manifold 14 is effected by asolenoid control valve 51. When valve 51 is open hydraulic pressure issupplied via non-return valve 53 and line 54 to supply line 52 in themanifold 14. When valve 51 is closed hydraulic fluid returns toreservoir 11 via line 55. A pressure relieve valve 56 is fed upstream ofcontrol valve 51 to determine the hydraulic pressure maintained in thesystem. This valve is usually set between 750 and 1000 psi anddischarges hydraulic fluid into return line 55 if the set pressure isexceeded. Manifold 14 thus provides hydraulic pressure to the flowcontrol valves 16 which in turn supply pressure to solenoid valves 15.Actuation of the solenoid valves 15 allows fluid to flow to hydrauliccylinders 17 to effect operation in the usual way. Thus actuation of thesolenoids 15 controls the operation of the cylinders 17 subject to theflow control of valves 16. The electronics module 18 provides electroniccontrol for the sequential operation of the solenoids according to thespeed of movement of the cultivator across the ground. The electroniccontrol module is of standard configuration and is not described indetail.

The operation of cultivator 1 is substantially conventional in that thevehicle is traversed across the surface to be aerated and the tines 20are operated to provide holes. The control of the hydraulic cylinders 17by electronic module 18 ensures that the desired hole spacing along thedirection of movement is achieved. FIGS. 7 to 11 show the sequentialsteps of operation of each of the linkage assemblies 19.

Referring to FIG. 6, the linkage assembly 19 is shown in a start orinitial rest position at the beginning of the aeration cycle. Thecylinder 17 and bias member 41 ensure that the follower 26 is at itslowest position towards the ground while the tool support member 34 israised above the ground surface. Reference numeral 46 indicates theinitial position of the support frame 2 with respect to the groundsurface.

At the next part of the aeration time cycle, as shown in FIG. 7, thecylinder 17 forces link arm 31 down towards the ground surface. Thiscauses tool support member 34 to move downward vertically, driving thecultivation tool 20 towards the ground surface. Due to the parallelogramstructure of the follower-tool support arrangement, the force applied bythe cylinder 17 to link arm 32 is transmitted to link arm 33 and toolsupport member 34 while the follower 26 remains stationary. As link arm33 moves in unison with link arm 32, the tool support member 34 is madeto move downwards in a straight line, ensuring that the cultivation tool20 moves perpendicularly into the ground surface. The support frame 2 inthis time has moved distance of 22 mm from its initial point 46.

FIGS. 8 and 9 illustrate the mid and full depth positions of aerationtime cycle respectively. The cylinder 17 continues to apply force on thetool support member 34 via link arms 32, 33 so that the cultivation tool20 penetrates the ground surface to most of its full length, forming thehole. The depth of the hole is determined by the extension of cylinder17.

It can be seen that after engaging the ground surface, the cylinder 17swings around pivot point 38 as the support frame 2 continues to moveforward relative to the cultivation tool 20. There is a horizontalcomponent of motion involved and the pivot point 38 allows the cylinder17 to move the tine 20 (via link arms 32, 33 and tool support member 34)further from the support frame 2 in the horizontal direction. Thefollower 26 also moves in a linear fashion in a generally horizontaldirection, allowing the support frame 2 to move laterally away from thetool support member 34. As pivot point 38 is the initial start point forthe extension of the cylinder 17, pivot point 38 limits the maximumhorizontal distance (relative to support frame 2) that cylinder 17 maymove link arms 32,33.

It should also be noted that the cylinder extension is initiallydownward as the link arms 32, 33 are driven towards the ground surface.After the cultivation tool or tine 20 engages the ground surface, themovement of the cylinder 17 becomes more inclined as the support frame 2continues its horizontal movement. Referring to FIGS. 6 to 8, the angleof the cylinder 17 relative to the vertical increases from initially 19°to a maximum of 40°. The increase in the angle of the cylindercorresponds to the increase of the horizontal distance from of about 87mm between the support frame 2 and the cultivation tool 20.

The link arm arrangement is particularly useful in providing increasingdistance between the tool support member 34 and the support frame 2 whenthe second pair of link arms 32, 33 move below a horizontal positiontowards the ground surface. From the rest position when the cultivationtool 20 is uppermost and the link arms 32, 33 are angled upward untilwhen link arms 32, 33 become horizontal, the tool support member 34 ismoving away from the support frame 2 as the frame 2 moves forward. Whenthe link arm 32 moves below the horizontal then the tool support 34starts to swing in an arc back towards the frame 2, reducing thedistance between the tool support member and the frame 2. During thisstage the parallelogram structure itself drifts away from the supportframe 2 to compensate for this swing towards the support frame 2. Oncethe cultivation tool 20 is at full depth and in the withdrawal phase,the tool support member is moving away from the support frame 2 relativeto the ground and so no drift by the parallelogram is needed, althoughthe drift of the parallelogram structure effected by link arms 24, 25 isconstantly compensating and providing accurate lateral movement at alltimes. The parallelogram structure of the follower-tool supportarrangement is required to drift during the period between the link arms32, 33 being horizontal and the tool 20 is at full depth penetration.That is, when link arms 32, 33 are below the horizontal.

As the support frame 2 continues to move horizontally along the groundsurface, the horizontal component of motion is transmitted to link arm25, causing pedal 42 to engage bias member 41. The force arising fromthe horizontal movement of the support frame 2 distorts the bias member41 so as to accommodate this horizontal force so that the cultivationtool or tine 20 remains stationary to form a vertical hole. That is,bias member 41 acts against the force applied by the support frame 2once the cultivation tool or tine 20 engages the ground. Consequently,the bias member 41 will apply a restoring force via pedal 42 to assistin returning link arms 32, 33, follower 26 and tool support 34 to therest position.

Referring to FIG. 10, once the hole of required depth has been formed,the withdrawal phase of the aeration time cycle begins. The cylinder 17now applies a pulling force on the link arm 32. This pulling forcecauses link arm 32 to rise in an inclined angle towards the restposition. This pulling force is transmitted to the tool support member34 via parallel link arms 32, 33 causing the cultivation tool 20 towithdraw from the ground surface until it is clear of the ground surface(see FIG. 11). Thus, the alignment of cylinder 17 moves follower 26 andlink arms 32, 33 through the required angle in both the downward andupward strokes of the aeration time cycle, respectively.

In addition, the bias member 41, which has been distorted byaccommodating the horizontal force arising from the increased horizontaldistance between support frame 2 and cultivation tool 20, returns to itsinitial shape. This restoring force applied by the bias member 41assists in returning follower 26 and tool support 34 to the restposition. Stop 44 ensures that the cylinder 17 does not completely closeon the upstroke of the withdrawal phase to prevent wear and damage tothe retraction of the cylinder 17 when the follower-tool supportarrangement returns to the rest position. The assembly 19 is then readyfor the aeration time cycle to begin again.

During the whole aeration time cycle (i.e. the cultivation tool/tine 20being forced towards, penetrating into and withdrawing from the groundsurface), the cultivating device continues to move along the groundsurface. At all times during the aeration time cycle, the tool supportmember 34 and cultivation tool 20 are kept perpendicular relative to theground surface as the parallelogram structure of the follower-toolsupport arrangement in effect “stretches” lengthwise to compensate forthe increasing distance between the tool support member 34 and supportframe 2. In contrast, the known cultivating device relies on the linkarm joining the tool support member to the support frame to compensatefor the relative horizontal movement of the support frame.

Under control of module 18 the hydraulic circuit 51 can adjust thefrequency in which the cylinders 17 apply force to the link arm 32 sothat the operative phase can be varied as required. A higher frequencymeans a shorter aeration cycle so that the tool support member 34 movesmore often, resulting in more holes being formed by the cultivation tool20 in a given surface area.

A cultivating device was made in accordance with the present inventionhaving the same features as the preferred embodiment described above.The cultivating device used a 25 horsepower motor and traversed 5 m in24 seconds with holes being formed 100 mm apart. The cultivating deviceused four driver-followers with two vertical tines mounted on each ofthe tool support members. The hydraulic circuit was set with an aerationtime cycle of 120 “shots” (i.e. penetrations of the ground surface) perminute. It was found that the tines could make deeper holes of 8″ to10″, whereas holes made by machines of a similar scale and power were ofabout 5″ to 6″ deep.

FIGS. 12 and 13 illustrate the situation where one of the cultivationtools or tines strikes an obstruction during the operative phase of theaeration time cycle. In this event adjustable relief pressure control onthe hydraulic system via the control circuit 51 limits the load on thecultivation tool 20. As the hydraulic cylinders 17 operate by time, thecultivating device can compensate for the cultivation tool 20 strikingan obstruction 47 underneath the ground surface, such as a rock. When atine 20 strikes an underground obstruction 47, the circuit 51 detectsthat the load limit has been reached by means of relief valve 56. Thisstops cylinder 17 applying any greater downward force on the toolsupport member 34 and stopping cultivation tool 20.

The circuit 51 maintains the position of the cylinder 17 until thewithdrawal phase. The cylinder 17 then withdraws the tool support member34 and cultivation tool 20 in the usual way the aeration time cycle canbegin again on a fresh part of the ground surface.

Although the circuit 51 stops movement of the attached cylinder 17 untilthe withdrawal phase begins, the aeration time cycle continuesuninterrupted for the other tines 20 and the support frame 2 is free tocontinue its horizontal movement. That is, the other tines 20 continueto operate normally in their operative phases as the support frame 2continues its horizontal movement as part of the aeration time cycle.During the period when the cylinder 17 is stopped, there is norestriction to the extension of the follower-tool support arrangement toaccommodate forward motion of the support frame. This ensures that anyparticular follower—tool support arrangement can reset itself to therest position after striking an obstruction.

None of the known cultivating devices provides for detecting acultivation tool striking an obstruction and/or halting the cylinderwhile the aeration time cycle continues for other cultivation tools aswell as allowing for the support frame to continue its horizontalmovement. Therefore, in contrast to the prior art, this embodiment inaccordance with the invention pauses the cylinder where a tine strikesan obstruction, allowing the aeration time cycle to continue until thewithdrawal phase begins and so does not interfere with subsequentaeration time cycles.

In addition, alternative drivers other than hydraulic cylinders can beused to drive the follower. Such drivers include pneumatic systems,mechanical drivers and other drivers known to a person skilled in theart.

FIG. 14 shows a second embodiment of the present invention using amechanical driver. The link arm assembly 19 of this embodiment isidentical to that described in relation to FIGS. 1 to 13 and thedescription will not be repeated. The same reference numerals have beenused to identify corresponding features.

The cultivator 60 of the second embodiment is designed for attachment tothe three point linkage of a tractor (not shown). Support frame 2 ismodified to include upper and lower three point linkage attachments 61,62 of conventional type. The cultivator 60 is driven via an input shaft63 that is coupled with the power take off of a tractor (not shown).Input shaft 63 drives a gearbox 64 which in turn drives a pulley 65.Pulley 65 drives a jack shaft pulley 66 via conventional V-belt 67. Thejack shaft pulley 66 in turn drives a flywheel 68 using a conventionalV-belt 69. The flywheel 68 is thus driven in rotation by the power takeoff of the tractor in a conventional manner. A connecting rod 70 ispivotally connected at 71 with the flywheel 68 at a distance from itsrotational centre. The other end of connecting rod 70 is pivotallyconnected at 72 to link arm 32. It will be apparent that thisconfiguration results in the connecting of rod 70 reciprocally drivingthe link arm 32 in response to rotation of the flywheel 68. The flywheel68 is rotated anticlockwise when viewed in FIG. 14. This direction ofrotation provides a horizontal component to the movement of connectingrod 70 which generally aids the outward and inward movement of thelinkage assembly during the corresponding downward and upward movementof the tool 20. The extent of reciprocating movement is determined bythe size of the flywheel 68 and the radial distance of the point ofconnection 71 as well as the location of connection 72 to the link arm32. These parameters can be configured to provide the desired amount ofreciprocating movement. Adjustment of the speed of the power take offdrive determines the rate of reciprocating movement. Consequently themechanical drive can provide the same operation as the hydrauliccylinder of the first embodiment.

FIGS. 15 and 16 illustrate a third embodiment cultivating device 100having a revised dampening arrangement within a housing 130. In allother respects the cultivating device is the same as that shown anddescribed in FIG. 14. Although the cultivating device 100 is illustratedas a mechanically driven cultivating device, the dampening arrangementcan also be applied to other cultivating devices, such as thecultivating device shown and described in FIGS. 1 through 13.

FIGS. 15 and 16 illustrate the cultivating device in the same positionas shown in FIGS. 6 and 14. The position illustrated is at top of strokefor the tool support 34 and tine 20. According to the dampeningarrangement, the dampener 43, heretofore described in FIGS. 6 and 14, isreplaced with a dampening block 143. The bias element 41 is replacedwith a smaller vertical profile bias element 141 supported on a fixedblock 142. The profile of the arm 25 on which the pedal 42 is mountedprovides a cam surface 148 that contacts the dampening block 143.

The dampening block 143 can be mounted via a bracket 149 and fasteners(not shown) to the housing 130. Alternatively the block 143 could bemounted to the follower 26, to move with the follower 26. The dampeningblock 143 provides a contact surface 154 that is angled to besubstantially tangential to the cam surface 148. Preferably, a centerpoint 156 of a radius 158 of the cam surface, the radius 158 that passesthrough a midpoint 162 of the contact area of the cam surface 148 withthe block 143 (in the position shown in FIGS. 15 and 16), is offset by adistance d with respect to a pivotal axis 29 a of the arm 25. Accordingto one embodiment, this offset distance d can be 3 mm. This offsetprovides for a progressive frictional engagement of the cam surface 148with the block contact surface 154 as the arm rotates clockwise aboutthe axis 29 a. The offset also provides a progressive frictionalengagement of the cam surface 148 with the block contact surface 154 toprevent the arm 25 from rotating counter-clockwise about the pivot axis29 a. At the top of the stroke any tendency to rebound or bounce is thussubstantially impeded. This impedance is effected by the cam surface 148substantially preventing counter-clockwise rotation about the axis 29 a.Connecting rod 70 is in a neutral position and is not urging lateralmovement.

The bias element 141 expands and returns to its original shape as thelinkage returns to the top of the stroke. The bias element 141 assistsin forcing the pedal 42 to rotate clockwise in FIG. 16, to the fullreturn position shown. The bias element 141 is advantageously composedof urethane having a Shore hardness of 70A.

As the arm 25 rotates clockwise, the cam surface 148 of the arm 25progressively engages the dampening block 143 to progressively arrestclockwise rotation of the arm 25. The dampening block 143 is squeezedbetween the cam surface 148 on a front side and the follower 26 on arear side. Accordingly, the arm 25 comes to a controlled,frictionally-induced stop instead of substantially compressing thedampening block 143 which would otherwise cause a subsequentcounterclockwise rebound or bounce. The interaction of the cam surface148 and the block 143 prevents rebound of the arm 25 in acounter-clockwise direction, and this interaction is enhanced by thesqueezing or clamping of the block 143 between the cam surface 148 andthe follower 25. The dampening block 143 is made of a stiff material,such as urethane having a Shore hardness of 70D.

It can be appreciated that the system of a cam engagement of arelatively stiff surface to dampen movement induced by an expansion of abias element can be embodied in a number of alternate ways, allencompassed by the present invention.

The improved dampening arrangement is intended to enable the tine toutilize the full amount of lateral movement (“lateral” being along thedirection of travel of the cultivator along the ground surface) that anylinkage design affords.

The dampening arrangement of FIGS. 15 and 16, utilizing a bias elementand a cam-engaged dampening block, can also be effectively used in othercultivating device configurations, such as the devices disclosed in U.S.Pat. No. 5,988,290, herein incorporated by reference. Particularly, thebuffer arrangement depicted in FIGS. 7 and 8 of U.S. Pat. No. 5,988,290could be replaced by a bias element and cam-engaged dampening block inaccordance with the present invention.

The dampening configuration of FIGS. 15 and 16 is advantageous in thatit reduces or eliminates “bounce” when the tool support returns to thetop of the stroke. Bounce is a problem that has been particularlyencountered with mechanical versions of the cultivating device whichoperate at a higher speed than hydraulic versions. This bouncedisadvantageously causes the linkage arm to commence the downstroke inan already advanced position. Significant amounts of bouncedisadvantageously reduces the advancement distance that can be achievedwhile still maintaining adequate ground surface finish and hole quality.

The tool support member may support any type of cultivation tool, suchas a fork having several tines or a single tine. Other attachments maybe employed by the tool support member as required.

The components of the cultivating device are generally made of metal,such as the support frame, follower, tool support member and cultivationtool. Other suitable resilient materials may be used to manufacture thecomponents of the cultivating device.

From the foregoing, it will be observed that numerous variations andmodifications may be effected without departing from the spirit andscope of the invention. It is to be understood that no limitation withrespect to the specific apparatus illustrated herein is intended orshould be inferred. It is, of course, intended to cover by the appendedclaims all such modifications as fall within the scope of the claims.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgment or any form of suggestion that thatprior art forms part of the common general knowledge.

1. A cultivator for aerating a ground surface including: a support framemoveable relative to the ground surface generally along a firstdirection; a tool support member connected to said support frame by atleast two links, a first link pivotally connected the tool supportmember at one end and pivotally connected to a second link at anopposite end, said second link pivotally connected to said supportframe, said tool support member operable along a second directionsubstantially perpendicular to the first direction; a driver toselectively effect cyclic movement of the tool support member in saidsecond direction; a bias element to provide resilient damping of thepivoting movement of said second link in a first rotary direction; and adampening element to provide resilient damping of the pivoting movementof said second link in a second rotary direction opposite said firstrotary direction, to progressively arrest pivoting movement of thesecond link in the second rotary direction.
 2. A cultivator as claimedin claim 1 wherein said driver includes a mechanical arrangement whichimparts reciprocating movement to one of the link arms.
 3. A cultivatoras claimed in claim 2 wherein said driver includes a rotating flywheeland a connecting rod mounted to move reciprocally in response torotation of the flywheel.
 4. A cultivator as claimed in claim 1, whereinsaid dampening element comprises a cam surface formed on said secondlink and a dampening block arranged to progressively engage said camsurface upon pivoting movement of said second link.
 5. A cultivator foraerating a ground surface including: a support frame moveable relativeto the ground surface; a follower pivotally connected to the supportframe by a first pair of spaced link arms having two pairs ofequidistantly spaced pivot points for linear movement of the followeralong a first direction toward and away from the support frame; a toolsupport member pivotally connected to the follower by a second pair ofspaced link arms having two pairs of equidistantly spaced pivot pointsfor linear movement of a cultivating tool along a second directionsubstantially perpendicular to the first direction; and a driver toselectively effect cyclic movement of the tool support member along saidsecond direction and effect movement of the follower along said firstdirection; a bias element to provide resilient damping of the movementof said follower along said first direction away from said supportframe, wherein said resilient damping is provided at an extremity ofmovement of the follower outward from the support frame along said firstdirection to urge the follower in the direction of inward movementtoward said support frame; and a dampening element to provide resilientdamping of the movement of said follower along said first directiontoward said support frame, said resilient damping provided at anextremity of movement of the follower inward toward the support frame insaid first direction to progressively arrest movement of the follower inthe direction of inward movement toward said support frame.
 6. Acultivator as claimed in claim 5 wherein said first direction issubstantially parallel to said ground surface and said second directionis substantially perpendicular to said ground surface.
 7. A cultivatoras claimed in claim 5 or claim 6 wherein said first pair of link armsmaintain said follower in a substantially constant orientation to saidsupport frame.
 8. A cultivator as claimed in any one of claims 5 to 7wherein said follower, said second pair of link arms and said toolsupport member substantially form the respective sides of aparallelogram.
 9. A cultivator as claimed in any one of claims 5 to 8wherein said driver acts on one of said second link arms.
 10. Acultivator as claimed in claim 9 wherein said driver is a linearlyoperable device acting between said support frame and one of said secondlink arms.
 11. A cultivator as claimed in claim 10 wherein said driveracts in a direction substantially parallel to the direction between thespaced pivot points of one of said first link arms.
 12. A cultivator asclaimed in claim 11 wherein said first link arms include an upper linkarm and a lower link arm, said upper link arm being positioned adjacentsaid driver.
 13. A cultivator as claimed in claim 12 wherein saidsupport frame includes a fixed support arm to which both said upper linkarm and said driver are connected.
 14. A cultivator as claimed in claim13 wherein said linearly operable device is a hydraulic cylinder.
 15. Acultivator as claimed in claim 12 wherein said lower link arm is bent toform an obtuse angle.
 16. A cultivator as claimed in claim 5 whereinsaid bias element acts against an extension of one of said first linkarms.
 17. A cultivator as claimed in any one of claims 5 to 16 whereinone or more of said first and second link arms is formed by two parallelelements.
 18. A cultivator as claimed in any one of claims 5 to 9wherein said driver includes a mechanical arrangement which impartsreciprocating movement to one of the link arms.
 19. A cultivator asclaimed in claim 18 wherein said driver includes a rotating flywheel anda connecting rod mounted to move reciprocally in response to rotation ofthe flywheel.
 20. A cultivator as claimed in claim 5, wherein saiddampening element comprises a cam surface formed on one of said firstlink arms and a dampening block arranged to progressively engage saidcam surface upon pivoting movement of said first link arm.
 21. Acultivator as claimed in claim 20, wherein said dampening block is sizedand positioned to be squeezed between said cam surface and said followerwhen said tool support member is raised in said second direction.